Freescale Semiconductor - NXP

The 74LVC163 is a synchronous presettable binary counter which features an internal look-ahead carry and can be used for high-speed counting. Synchronous operation is provided by having all flip-flops clocked simultaneously on the positive-going edge of the clock (pin CP). The outputs (pins Q0 to Q3) of the counters may be preset to a HIGH-level or LOW-level. A LOW-level at the parallel enable input (pinPE) disables the counting action and causes the data at the data inputs (pins D0 to D3) to be loaded into the counter on the positive-going edge of the clock (provided that the set-up and hold time requirements for PE are met). Preset takes place regardless of the levels at count enable inputs (pin CEP and CET). A LOW-level at the master reset input (pinMR) sets all four outputs of the flip-flops (pins Q0 to Q3) to LOW-level after the next positive-going transition on the clock input (pin CP) (provided that the set-up and hold time requirements for PE are met). This action occurs regardless of the levels at input pinsPE, CET and CEP. This synchronous reset feature enables the designer to modify the maximum count with only one external NAND gate.

The 74LVC1G00-Q100 is a single 2-input NAND gate. Inputs can be driven from either 3.3 V or 5 V devices. This feature allows the use of these devices as translators in mixed 3.3 V and 5 V environments. Schmitt-trigger action at all inputs makes the circuit tolerant of slower input rise and fall times. This device is fully specified for partial power down applications using IOFF. The IOFFcircuitry disables the output, preventing the potentially damaging backflow current through the device when it is powered down.